General Question

Can you kill whatever popped your jam (botulism?) through cooking or freezing?

My housemate noticed today that one of our jars of jam had a popped top. We would seriously hate to lose half our jam, so is there any way to safely consume it? Or do we just have to toss it? Would freezing or boiling or baking work or will the toxins still be there and nasty, though dead?

Baking/boiling will work to kill some pathogenic organisms, for example E. coli, but Clostridium botulinum (the bacterium that creates botulinum toxin) are very heat resistent, and can be boiled for long periods of time and not die. The botulinum toxin itself will degrade when heated, but the food is still not safe because the bacteria are still present. And honestly I wouldn’t trust it anyway… Botulinum toxin is the most acutely toxic substance known. 90–270 nanograms is the lethal dose in an average human. That’s 0.00000009 to 0.00000027 grams.

Also, I wouldn’t try to save the jar. To destroy the C. botulinum spores I believe you’d need to bake the jar at a temp of several hundred ºF for a while – and anything that came into contact with the contents of the jar would be tainted and need to be cleaned thoroughly before it would be safe for human contact. I would throw out the jar without opening it. (If you really really want to save your jar, use gloves and treat it like you’re cleaning up toxic waste!!! Throw the gloves out after. Maybe double-bag them, and the jam.)

Jams and fruit preserves are prone to mold if they’re not processed perfectly, but they’re not high risk for botulism. The classic scenario for botulism is a low acid vegetable like green beans. Fruit is acidic and botulism spores don’t like acid. Here’s a link that explains it in boring scientific detail.

I can occasionally and limit myself to low risk foods like jam and tomatoes. My mom on the other hand, used to can everything including green beans and corn which are both high risk foods. And she used the open kettle method, which is dangerous, because that’s what she learned growing up on the farm. She of course didn’t want to hear what I had learned about new fangled canning methods. So grateful she didn’t kill dad or herself.

Mash raspberries through sieve, throwing away seeds. Add sugar to raspberries and heat in saucepan to almost boiling. Mix cornstarch with cold water. Add cornstarch mixture little bit at a time to raspberries, stirring constantly, until mixture starts to thicken. Cool in refrigerator and serve with just about anything.

Okay. Honestly, this sounds like a bit of an exaggerated concern. I have had botulism occur in my canned green beans and recently in my beautiful beets. Only on the shelf for 6 weeks, when opened, fizzed like seltzer for at least 5 minutes. the explosive gases spelled Botulism to me. IF it is clearly so common in these starchy low acid foods, then the spores are probably on fresh corn, beets and beans to begin with. We probably eat the spores routinely since many of us canning type people do eat a lot of fresh stuff that is cooked lightly. Unless Botulaism spores are spontaneously generated at the Ball jar factory, we are eating them. So, as for throwing out my jar while wearing a hazmat suit, I am going to do as I always do and wash the jars better than I might have before, for using again. Too late for paranoia now, cuz I spilled some in a sink full of stuff.
Don’t want fear as a hobby no mo’
Bigtime canner

The botulism spores are not dangerous It’s the paralytic toxins produced by the spores under the right wrong circumstances. For home canners, it’s usually low acid foods that aren’t heated to a high enough temperature for long enough. If the spores survive the canning process, they start producing the toxin in the airless environment of the sealed jar/can. Foods contaminated with botulism toxin can look normal and smell normal. The best way to be safe is to use pressure canning techniques for meats and low acid foods. I speak as the daughter of a long time “open kettle method” canner who survived despite my mother’s resistance to those new fangled scientific warnings.

Based on my (limited) research, you cannot detect if botulism has caused problem in the food – it doesn’t change at all. The indication, according to http://wiki.answers.com/Q/What_are_the_signs_of_botulism_in_home_canned_foods, of botulism in your jam is that people get sick and/or die. Just because it goes bad doesn’t mean that it’s botulism. Most botulism cases in the US are found in Alaska (around 40%) and mostly in meat and fish products canned by the natives, not because they are natives, but probably because they can meat and fish! It seems that all fruit and vegetables contain botulism spores to some degree. Acidity seems to prevent them from giving off toxins.

There are mathematical rules to how long and at what temperatures food should be cooked to kill the Clostridium botulinum bacteria. See http://www.nzifst.org.nz/unitoperations/httrapps2.htm for detailed information. Botulism does not create mold on top, that is completely different and completely unrelated and is probably not going to kill anyone. It was common with jam (rhubarb mostly, but also blueberry) that my mom made that it would get a layer of mold on top – we scraped it off and ate the rest and it never affected anyone. She would cook it for hours and she’d put the jars in the oven for an hour or so before putting the jam in. She never sealed the jars with anything except just a screw-on lid and the jars were used over and over again for years.

While it is certainly extremely important to maintain good hygiene in the kitchen at all times and prevent any kind of cross-contamination, people should be careful to not get too paranoid. People have been making jams for hundreds of years with much less hygiene than we can even think of and enough of them made it through to make us:) The first jams came to Europe from the Middle East during the middle ages and in the late 17th century books were being published here in the US about how to make jams. Botulism wasn’t discovered for another two centuries and nobody had pressure cookers or cans, but somehow people made jam and survived:)